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Evil Reostat!
- Thread starter Tomsawyer
- Start date
I recently hooked up a YS-Tech 120mm 3wire fan with the power connected thru a rheostat to the PS, and the tach wire to the mobo header (CUSL-2). When the fan is up full, the BIOS (and MBM5) don't report the fan's rpm (BIOS says n/a, and MBM5 says 0 rpm). When I turn the fan speed down, the fan speed starts to register, but is incorrect. (the fan is rated 2800 rpm, but starts to show in both BIOS & MBM5 at about 5000 with the rheostat turned down about halfway).
Any ideas??
Any ideas??
- Joined
- Dec 18, 2000
- Location
- North Carolina
Changing to a 150 ohm rheostat may not make any difference and will probably make things worse- you want to increase the power rating, not change the resistance. Get a 5 watt part instead of a 1 or 2 watt or else it will likely happen again.
I got my 25 Ohm Rhestat from Radioshack for 2.99 each. They are connected to Panaflo 120mm fan and works just fine. This panaflo fans are rated at 5~6watt and the 25 Ohm rheostat from radiashack is rated about the same.5.5 or 5.6 watt total. So as long as you have proper watt power, you'll be fine.
Go to the Shack an buy a LM317 voltage regulator. The circuit is on the back of the package. Put a 1uf elctrolytic cap and a .1uf ceramic cap on the output and a .1uf and .01uf ceramic caps on the input. This is the professional way of dealing with fan speed. Rheostats suck.
Yea...but what about people who don't really know the "professional" way you're talking about? I believe that if the rheostat works just as fine as the "professional" voltage meter you're talking about, why go through all that trouble? It saves money as well.
Tom,
Rheostats are a dirty way of dealing with voltage. In the extreme imagine a block of dry ice as a CPU cooler. They have mechanical parts that will eventually fail compared with a reliable electronic voltage regulator. The overall cost is very close. It’s the human time and effort that makes the difference. When I get back from my vacation next week, I would be happy to help you with building a multiple LM317 circuit.
Colin
Rheostats are a dirty way of dealing with voltage. In the extreme imagine a block of dry ice as a CPU cooler. They have mechanical parts that will eventually fail compared with a reliable electronic voltage regulator. The overall cost is very close. It’s the human time and effort that makes the difference. When I get back from my vacation next week, I would be happy to help you with building a multiple LM317 circuit.
Colin
Pots have three terminals too. From the back, center is common, right gives increasing resistance with clockwise rotation, left gives increasing resistance with counterclockwise rotation. Rheostats are just wire wound pots that can handle more current. Solid state devices are still a better choice for voltage regulation.
